scholarly journals DETERMINATION OF DEFORMABILITY PARAMETERS OF CONCRETE SAMPLES BY THE FORMULAS OF FRACTURE MECHANICS

2020 ◽  
Vol 11 (2) ◽  
pp. 88-98
Author(s):  
B. A Bondarev ◽  
N. N Chernousov ◽  
V. A Sturova
Keyword(s):  
Fracture Mechanics ◽  
Lower Surface ◽  
Local Deformation ◽  
Concrete Sample ◽  
Test Scheme ◽  
Limit Value ◽  
Bending Load ◽  
Internal Forces ◽  
The Moment ◽  
External Forces

To determine the deformability parameters of concrete samples by the formulas of fracture mechanics, equilibrium tests were carried out at the stage of local deformation of the sample, which showed the correspondence of the change in external forces to the internal forces of the material resistance with the corresponding static development of the main crack. For the same purpose, the samples are tested for bending with an initial notch and the “load-deflection” diagram is recorded. In this work, we presented a test scheme for a specimen with a notch (crack) and constructed a diagram of the deformation of a specimen under bending “load-deflection”. Based on it, it is possible to predict the destruction of the material, that is, to determine the value of the load at which the limit value of deflection or the displacement of the outer edges of the notch (opening the throat of the crack on the lower surface of the specimen) can be taken as the moment of loss of the resource of the material. Also, we examined the deformation of a concrete sample during three-point bending and presented a diagram of the deformation of a concrete sample within the plastic zone. Dependencies were derived for determining the ultimate relative strains under tension and bending. Based on the results obtained, the state diagrams of the stretched concrete and the deformation scheme of the normal section of the concrete sample were constructed. As a result, the conclusion and convergence of the results.

scholarly journals Deflection prediction of cantilever concrete beam using adaptive fuzzy inference system

2018 ◽  
Vol 7 (2.2) ◽  
pp. 108
Author(s):  
Sujiati Jepriani ◽  
Ibayasid . ◽  
Aji Prasetya Wibawa ◽  
Leonel Hernandez
Keyword(s):  
Fuzzy Logic ◽  
Fuzzy Inference System ◽  
Concrete Beam ◽  
Fuzzy Inference ◽  
Initial Position ◽  
Training Data ◽  
Inference System ◽  
Internal Forces ◽  
The Moment ◽  
External Forces

The cantilever concrete beam is a beam made of concrete that is only supported or clamped at one end and the other end free or without the pedestal. The measure to which a structural member gets deviated from the initial position is called deflection. All the internal forces of cantilever beam serve to hold all the external forces due to the load so that the structure remains balanced. While the beam gets deflected under the loads, bending occurs in the same plane due to which stresses are developed. From the moment balance formula after integrated and solved with required boundary conditions, we get the downward deflection of beam. Fuzzy logic provides an inference structure that enables appropriate human reasoning capabilities. FIS (Fuzzy Inference System) is a system that processes the mapping formulation of a given input to produce an output using Fuzzy Logic. By using randomized data for all the variables of deflection formula within their respective ranges as training data, the FIS will be able to predict deflection of cantilever concrete beam after going through the training process adaptively.  

scholarly journals Elastic Simulation of Joints with Particle-Based Fluid

2021 ◽  
Vol 11 (15) ◽  
pp. 6900
Author(s):  
Su-Kyung Sung ◽  
Sang-Won Han ◽  
Byeong-Seok Shin
Keyword(s):  
Principal Stress ◽  
Human Body ◽  
Yield Condition ◽  
Maximum Principal Stress ◽  
Human Motion ◽  
The Difference ◽  
The Moment ◽  
External Forces ◽  
Physical Changes ◽  
Elastic Simulation

Skinning, which is used in skeletal simulations to express the human body, has been weighted between bones to enable muscle-like motions. Weighting is not a form of calculating the pressure and density of muscle fibers in the human body. Therefore, it is not possible to express physical changes when external forces are applied. To express a similar behavior, an animator arbitrarily customizes the weight values. In this study, we apply the kernel and pressure-dependent density variations used in particle-based fluid simulations to skinning simulations. As a result, surface tension and elasticity between particles are applied to muscles, indicating realistic human motion. We also propose a tension yield condition that reflects Tresca’s yield condition, which can be easily approximated using the difference between the maximum and minimum values of the principal stress to simulate the tension limit of the muscle fiber. The density received by particles in the kernel is assumed to be the principal stress. The difference is calculated by approximating the moment of greatest force to the maximum principal stress and the moment of least force to the minimum principal stress. When the density of a particle increases beyond the yield condition, the object is no longer subjected to force. As a result, one can express realistic muscles.

Crack Propagation Simulation: A Local Deformation-Based Mesh Mapping Method for Crack Modeling and a Direct Method for Residual Stress Representation in Welds

2011 ◽  
Author(s):  
Heqin Xu ◽  
Samer Mahmoud ◽  
Ashok Nana ◽  
Doug Killian
Keyword(s):  
Finite Element ◽  
Fracture Mechanics ◽  
Stress Corrosion ◽  
Stress Corrosion Cracking ◽  
Crack Front ◽  
Direct Method ◽  
Local Deformation ◽  
Front Shape ◽  
A Direct Method ◽  
Mesh Mapping

Cracks found in a nuclear power plant reactor coolant system (RCS), such as primary water stress corrosion cracking (PWSCC) and intergranular stress corrosion cracking (IGSCC), usually have natural crack front shapes that can be very different from the idealized semi-elliptical or rectangular shapes considered in engineering handbooks and other analytical solutions based on limited shapes. Simplifications towards semi-elliptical shape or rectangular shape may potentially introduce unnecessary conservatism when the simplified shape has to contain the actual crack shape. On the other hand, it is very time-consuming to create a three-dimensional (3D) finite element (FE) model to simulate crack propagation in a natural shape using existing public-domain software like ABAQUS or ANSYS. In this study, a local deformation-based mesh-mapping (LDMM) method is proposed to model cracks with a natural front shape in any 3D structures. This methodology is first applied to model circumferential surface cracks with a natural crack front shape in the cross-sectional plane of a cylinder. The proposed new method can be applied to simulate both shallow and deep cracks. Also discussed in this paper is a direct method to reproduce welding residual stresses in the crack model using temperature fields combined with other sustained loads to predict crack propagations. With this novel LDMM method, natural crack fronts and non-planar crack faces can be easily modeled. The proposed new method can be used to generate a high-quality finite element model that can be used for both linear-elastic fracture mechanics (LEFM) and elastic-plastic fracture mechanics (EPFM) analyses. The study case illustrates that the proposed LDMM method is easy to implement and more efficient than the existing commercial software.

Application of Fracture Mechanics to Steel Connections in Moment Frames under Seismic Loading

1997 ◽  
Vol 1 (1) ◽  
pp. 23-37 ◽  
Author(s):  
C. Joh ◽  
W.F. Chen
Keyword(s):  
Fracture Mechanics ◽  
Steel Structures ◽  
Northridge Earthquake ◽  
Moment Frames ◽  
Moment Connections ◽  
Related Factors ◽  
Steel Connections ◽  
Moment Connection ◽  
San Fernando ◽  
The Moment

The 6.8 magnitude Northridge earthquake that shook California's San Fernando Valley on January 17 in 1994, did not cause the collapse of any steel structures but connections, confidently designed and constructed in the past with traditional code simplification and common site welding techniques, were discovered not to meet our expectations. This paper reviews connection failures during the 1994 Northridge earthquake and the design philosophy and examines the post-Northridge earthquake experimental and analytical researches. Possible causes of the moment connections damage are categorized into three classes; welding-related factors, design-related factors, and material-related factors. For the analyses, the idealizations of the moment connection considering each factor are studied. From the idealization of the moment connection, the five-plate model is analyzed to investigate the stress concentration and stress state of the connection. The equivalent design crack models are investigated using the fracture mechanics approach.

scholarly journals Job Opening for Nucleosome Mechanic: Flexibility Required

Cells ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 580 ◽  
Author(s):  
Mary Pitman ◽  
Daniël P. Melters ◽  
Yamini Dalal
Keyword(s):  
Mechanical Properties ◽  
Computational Modeling ◽  
Chromatin Fiber ◽  
Interdisciplinary Approaches ◽  
External Cues ◽  
Internal Forces ◽  
Innovative Work ◽  
External Forces ◽  
Chromatin Biology

The nucleus has been studied for well over 100 years, and chromatin has been the intense focus of experiments for decades. In this review, we focus on an understudied aspect of chromatin biology, namely the chromatin fiber polymer’s mechanical properties. In recent years, innovative work deploying interdisciplinary approaches including computational modeling, in vitro manipulations of purified and native chromatin have resulted in deep mechanistic insights into how the mechanics of chromatin might contribute to its function. The picture that emerges is one of a nucleus that is shaped as much by external forces pressing down upon it, as internal forces pushing outwards from the chromatin. These properties may have evolved to afford the cell a dynamic and reversible force-induced communication highway which allows rapid coordination between external cues and internal genomic function.

scholarly journals Evaluation of Health Risk Level of Hand-Arm and Whole-Body Vibrations on the Technical Operators and Equipment in a Tobacco-Producing Company in Nigeria

2019 ◽  
Vol 2019 ◽  
pp. 1-12
Author(s):  
Oluseyi Adewale Orelaja ◽  
Xingsong Wang ◽  
Dauda Sh. Ibrahim ◽  
Umer Sharif
Keyword(s):  
Whole Body ◽  
Risk Level ◽  
Time Frequency ◽  
Daily Exposure ◽  
Limit Value ◽  
Exposure Limit ◽  
High Acceleration ◽  
External Forces ◽  
Secondary Manufacturing ◽  
Iso 2631

Vibration is experienced when a body is subjected to either internal or external forces which cause oscillation, with most operators of industrial equipment often exposed to high dosage, higher than the stipulated values. In this research, Digital Real-Time Frequency Analyzer (RSA 5106A) was used, while the results obtained were evaluated and compared with the health guidelines of the ISO 2631-1 : 1997 and ISO 2631-5 : 2004 standards, as described in the Health Guidance Caution Zone for a daily exposure action value (EAV) of 0.47 m/s2 and a daily exposure limit value (ELV) of 0.93 m/s. High acceleration was mostly seen on the z-axis in all the results obtained, whereas many were not within the HGCZ (Arms <0.47, and >0.93 m/s2). Comparing (VDV <8.5 m/s1.75 and >17 m/s1.75) with the ISO standard, the accelerations on all x- and y-axes were slightly within the HGCZ, with just a little below 0.47 m/s2 limit. The results obtained clearly showed that urgent action is needed virtually on all the equipment in both the Secondary Manufacturing Department (SMD) and Primary Manufacturing Department (PMD) to minimize vibration exposure on the technical operators.

Dynamic Behavior Analysis of Mechanical Monoleaflet Heart Valve Prostheses in the Opening Phase

1993 ◽  
Vol 115 (4A) ◽  
pp. 389-395 ◽  
Author(s):  
Gill-Jeong Cheon ◽  
K. B. Chandran
Keyword(s):  
Heart Valve ◽  
Heart Valve Prostheses ◽  
Runge Kutta Method ◽  
Valve Opening ◽  
Valve Prostheses ◽  
The Moment ◽  
External Forces ◽  
The Impact ◽  
Open Position ◽  
Opening Phase

In this paper, fluttering behavior of a mechanical monoleaflet tilting disk heart valve prostheses during the opening phase was analyzed. The impact between the occluder and the guiding strut at the fully open position was included in the analysis with a Bjork-Shiley monoleaflet aortic valve. The motion of the valve occluder was modeled as a rotating system, and equations were derived by employing the moment equilibrium principle. Forces due to lift, drag, gravity, and buoyancy were considered as external forces acting on the occluder. The 4th-order Runge-Kutta method was used to solve the governing equations. The results demonstrated that the occluder reaches the steady equilibrium position only after damped vibration. Fluttering frequency varies as a function of time after opening and is in the range of 8–84 Hz. Valve opening appears to be affected by the orientation of the valve relative to gravitational force. The opening velocities are in the range of 0.56–1.37 m/sec and the dynamic loads by impact of the occluder and the strut are in the range of 60–190 N.

Mechanical state of airway smooth muscle at very short lengths

2004 ◽  
Vol 96 (2) ◽  
pp. 655-667 ◽  
Author(s):  
Richard A. Meiss ◽  
Ramana M. Pidaparti
Keyword(s):  
Smooth Muscle ◽  
Connective Tissue ◽  
Mechanical Behavior ◽  
Muscle Length ◽  
Muscle Stiffness ◽  
Smooth Muscle Tissue ◽  
Cross Bridge ◽  
Extracellular Matrix Components ◽  
Internal Forces ◽  
External Forces

Although the shortening of smooth muscle at physiological lengths is dominated by an interaction between external forces (loads) and internal forces, at very short lengths, internal forces appear to dominate the mechanical behavior of the active tissue. We tested the hypothesis that, under conditions of extreme shortening and low external force, the mechanical behavior of isolated canine tracheal smooth muscle tissue can be understood as a structure in which the force borne and exerted by the cross bridge and myofilament array is opposed by radially disposed connective tissue in the presence of an incompressible fluid matrix (cellular and extracellular). Strips of electrically stimulated tracheal muscle were allowed to shorten maximally under very low afterload, and large longitudinal sinusoidal vibrations (34 Hz, 1 s in duration, and up to 50% of the muscle length before vibration) were applied to highly shortened (active) tissue strips to produce reversible cross-bridge detachment. During the vibration, peak muscle force fell exponentially with successive forced elongations. After the episode, the muscle either extended itself or exerted a force against the tension transducer, depending on external conditions. The magnitude of this effect was proportional to the prior muscle stiffness and the amplitude of the vibration, indicating a recoil of strained connective tissue elements no longer opposed by cross-bridge forces. This behavior suggests that mechanical behavior at short lengths is dominated by tissue forces within a tensegrity-like structure made up of connective tissue, other extracellular matrix components, and active contractile elements.

Intensity Waves: External or Internal Forces?

2010 ◽  
Vol 437 ◽  
pp. 563-567
Author(s):  
Peter A. Kulichkin
Keyword(s):  
European Countries ◽  
Artistic Creativity ◽  
Term Trend ◽  
Artistic Style ◽  
Artistic Life ◽  
Internal Forces ◽  
External Forces ◽  
Long Term Trend

Periodical processes with duration of cycles about 50 years (MMP-waves), observed in artistic style, were deduced earlier. As well analogous waves take place in the intensity of artistic life, artistic creativity, and related spheres. On the basis of the data on 5982 composers, 867 painters, 2741 persons of theatre, and 992 playwrights of the 12th – 20th centuries (relating to 40 European countries), evolutionary curves were built for the ‘intensity of artistic creativity’ in each kind of art. Most curves reveal hill-like long-term trend; against the background of this trend periodical oscillations were observed, some of them being synchronous both for different kinds of art and different cultural regions. The same level of the intensity would be obtained if the value of external forces is rather high and the value of internal forces is low, or vice versa. Dealing with MMP-waves we can see 50-year cycles. Studying Intensity waves we observe cycles with various periods (about 40-50 years). Such difference is likely to be connected with influence of external and internal forces.

Nuts

1992 ◽  
Vol 292 ◽  
Author(s):  
Julian F. V. Vincent
Keyword(s):  
Fracture Mechanics ◽  
Selection Pressures ◽  
External Forces ◽  
Biological Selection

AbstractThe shell (pericarp) of nuts protects the seed from being eaten before it can germinate. It is presumably designed to resist fracture by external forces, and evolution will have optimised its design for this purpose. It appears that the material of larger shells, which will tend to be structurally more brittle, is tougher. However, the fracture mechanics theory for shells in compression is not available, nor the information on the biological selection pressures.

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